What is the Universe’s arrangement today? What did it look like at its birth? And how did we get from then to now? These are just some of the “Big Questions” astronomers are making headway answering.

There’s only one star that astronomers have a firm grasp on: the Sun. Fundamental facts about other stars remain elusive. Find out how a powerful interferometer atop Mount Wilson in Southern California hopes to change that.

Name any debacle of nature, and someone will likely blame it on El Niño. But there’s another large-scale climate pattern that's been overlooked: El Niño's fickle Nordic sister, the North Atlantic Oscillation.

Find out how each NAO phase spins its particular brand of atmospheric tumult, affecting temperature, precipitation, cloudiness, and windiness in different regions — sometimes to drastic ends.

From the chilly depths of the Atlantic to ancient European forests, researchers are combing for data to explain the NAO's mysteries.

Northern Hemispheric temperatures are now at their steamiest. Discover why scientists are concerned about global warming's potential backlash on the NAO.

Where would the world be without oxygen? While it's hard to imagine an Earth without it, for nearly the first half of the planet's 4.5-billion-year history, Earth had no oxygen gas as part of its atmosphere.

Where would the world be without oxygen? While it's hard to imagine an Earth without it, for nearly the first half of the planet's 4.5-billion-year history, Earth had no oxygen gas as part of its atmosphere.

One of the biggest forces that's shaped planet Earth over time is microscopic in size. Explore the global impact of microbes.

Discover how the geological and climatic changes that have unfolded over millions of years in Vietnam have set the stage for an extraordinary richness of biodiversity.